1. Field
The present invention relates to a robot and a method of controlling cooperative work thereof, and more particularly, to a robot, which performs cooperative work using a plurality of robot manipulators through impedance control, and a method of controlling cooperative work of the robot.
2. Description of the Related Art
In general, machines, which conduct motions similar to that of a human using an electric or magnetic action, are referred to as robots. Recently, robots have been applied to various fields due to development of a control technique. For example, there are housekeeping robots in homes, service robots in public facilities, transfer robots in industrial sites, and worker supporting robots. These robots perform work using manipulators, which are designed to conduct motions similar to that of an arm or a hand of a human through electrical and/or mechanical mechanisms.
Most robot manipulators, which are used now, include a plurality of links connected to each other. Connection parts between the links are referred to as joints, and motion characteristics of the manipulators are determined by the geometrical relation between the links and the joints. Kinematics mathematically expresses the geometrical relation. Robot manipulators having these kinematics characteristics respectively move end effectors thereof in a direction to perform work.
FIG. 1 illustrates a conventional method of performing cooperative work using robot manipulators.
As shown in FIG. 1, in order to remove a lid from a bottle by rotating the lid, at least two robot manipulators 1 and 3 are required, and in this case, the two robot manipulators 1 and 3 must perform cooperative work. In order to perform the cooperative work using the two robot manipulators 1 and 3, a control unit 5 calculates absolute positions of the two robot manipulators 1 and 3 by calculating trajectories of two end effectors 1-1 and 3-1, and calculates joint torques according to the positions and direction vectors of the two end effectors 1-1 and 3-1, thus respectively controlling the robot manipulators 1 and 3. Korean Patent Registration No. 0160693 discloses an example of the method of performing cooperative work using two robot manipulators.
However, in the conventional method of performing cooperative work using robot manipulators, since the positions and directions of the two end effectors 1-1 and 3-1 in respective absolute coordinate systems are required to calculate the trajectory of the robot, a user takes the positions and directions of the two end effectors 1-1 and 3-1 into consideration individually when a complicated cooperative work is performed, and thus is inconvenienced by the calculation. Further, if one robot manipulator 3 performs cooperative work when the other robot manipulator 1 grips an object and fixes the position of the object, a working space is restricted by the limit of joint angles.